59 Johnson 35hp Thermostat/ Cooling issues.

[sharkeydude]

Hey all, This is a great site and have really picked up a lot of tips so far and could use some help. I recently picked up a 59 Johnson 35hp RDS and am in the process of getting it back in the water. I replaced the impeller today (thanks to all the great posts here). I bucket tested and I still had no water coming from the exhaust, so, checked the thermostat.
There was no thermostat to check!
I know the impeller is working judging by the stream shot from where the thermostat should be. However, still no noticeable water expelled from the exhaust. When I blow in the tube where the thermostat was, I feel it coming from the exhaust. If I run water through it, no water comes out. I ordered a thermostat today. Is there something else I should check that doesn't necessarily involve getting into the engine itself?
I am perplexed.

 

[Bigkat650]

Re: 59 Johnson 35hp Thermostat/ Cooling issues.

It could just be something as simple as you do not have enough water in the tank to test. Your water has to be above the cavitation plate on those old 35's. Do you see where the lower unit bolts onto the leg? Water has to be over that seam--as that seam is not water tight. Basically the entire lower leg has to be in the water. It makes them a pain to test, but it has to be done

good luck and welcome!

 

[sharkeydude]

Re: 59 Johnson 35hp Thermostat/ Cooling issues.

Thanks for the reply. I had it in a garbage can, but the water wasn't as high as you mentioned. I'll take it to the ramp when I get the thermostat replaced and test it there. It runs really well. It does have a few misses here and there in low and does not want to idle smoothly. I'm in for a tune up for sure. I'm just hoping the cooling issues can be resolved so I can move to the next issue without too much trouble. Thanks again!

 

[Bigkat650]

Re: 59 Johnson 35hp Thermostat/ Cooling issues.

Thanks for the reply. I had it in a garbage can, but the water wasn't as high as you mentioned. I'll take it to the ramp when I get the thermostat replaced and test it there. It runs really well. It does have a few misses here and there in low and does not want to idle smoothly. I'm in for a tune up for sure. I'm just hoping the cooling issues can be resolved so I can move to the next issue without too much trouble. Thanks again!

That must be your problem then. Hope you didn't run it too long, it doesn't take long to do damage to an impeller without water going through. Odds are your OK, but its a cheap and easy thing to replace so you could consider checking that out. As far as your rough running idol, its probably a dirty carb or dirty plugs. You can clean both up for free, but should also replace the seals on the carb while your in there. Also its better to replace the plugs too rather then just cleaning them. Other things to check would be your high and low speed needles--more importantly the low speed. I believe it should be around a 1.5 turns from fully closed--that's your starting point anyways. Lastly, check your coils under the fly wheel. If they are cracked or weathered--they should be replaced. My guess is if you cleaned up those things, she will run good for years to come.

 

[sharkeydude]

Re: 59 Johnson 35hp Thermostat/ Cooling issues.

Wow, thanks for the step by step. I'm just getting to know boat motors. I wrench on my Harley every now and then so, its cool to see how another type of motor works. If I'm not careful though, I might get told to sleep in the boat since I love being with it so much, lol.

 

[kfa4303]

Re: 59 Johnson 35hp Thermostat/ Cooling issues.

Hi sharkey. This link should help.

http://www.duckworksmagazine.com/04/s/columns/max/24/index.cfm

 

[HighTrim]

Re: 59 Johnson 35hp Thermostat/ Cooling issues.

They wont pump right without the t stat and valve installed. I dont know why guys take them out.

 

[sharkeydude]

Re: 59 Johnson 35hp Thermostat/ Cooling issues.

They wont pump right without the t stat and valve installed. I dont know why guys take them out.

I re-read this post and think I found the problem! High Trim, I ordered a thermostat and put it in only to realize that I'm missing the spring, valve and seal! I need to read closer next time.
Parts on order, hoping this will solve my overheat issues once and for all!

 

[HighTrim]

Re: 59 Johnson 35hp Thermostat/ Cooling issues.

Im sure that will fix you up.

You will hear alot of guys on here say that the t stat and valve have no correlation with the pumping ability of the pump. They are wrong. That pump works great as a water pump, not so well as an air pump. Without that valve and t stat installed, exhaust and air get into the pump, destroying its ability to pump water. Some fellows remove them, thinking they are helping with water flow, when in fact they are making matters worse.

 

[sharkeydude]

Re: 59 Johnson 35hp Thermostat/ Cooling issues.

The $25 I spend will sure go a long way as opposed to a complete rebuild! I'll keep you posted! Thanks again!